The invention relates to an open end friction spinning machine with a plurality of spinning units which respectively each include two friction rollers driven in the same rotational direction and adjacently arranged to form a wedge slot therebetween. An inlet and opening device is provided for feeding of individual fibers to the wedge slot with a fiber feed channel connecting the inlet and opening device with the wedge slot. A withdrawal device is provided for withdrawing the formed yarn in the direction of the wedge slot and a suction device is provided for holding the existing or forming yarn in the wedge slot.
This application is related to application Ser. No. 604,373, filed on even date herewith and based upon the same German patent application P No. 33 15 034.6.
There is known a manually carried out start spinning procedure at a single spinning unit of an open end friction spinning machine wherein a yarn end is unraveled and is brought up to the fiber feeding position and is return guided via a yarn withdrawal tube into the closed spinning unit (European Published Application--EPOS No. 34427). There are special provisions provided at the spinning unit which should effect that the yarn end portion is held and at first takes an extended condition at a distance from the wedge slot. It should then be brought in the extended or stretched condition to the wedge slot. With this construction form, the necessary yarn end portion for the start spinning is in reality rotated inwardly at the circumference of the friction roller rotating into the wedge slot and is return guided alone by a suction device of the connected roller. These measures, which preceed the actual spinning process permit only a relatively inexact disposition of the return guided yarn end portion. There exists the danger that the previously spun yarn end portion is strung or gathered together during the transfer to the wedge slot in the reverse direction so that it takes an uncontrollable and undefined disposition. In this manner, the start spinning procedure is uncertain and unreliable. Above all, it is scarcely possible with such a problematical yarn guidance for the actual start spinning yarn connection to achieve the quality which is of such high value that it can remain in the yarn spool for the further processing.
The invention is based upon the problem to so construct an open end friction spinning machine with a plurality of spinning units that the return guided yarn end for the actual start spinning operation is so positioned after the return guidance that it is disposed in an exactly defined position which offers the best possibilities for the continuing processing of the actual start spinning operation.
This problem is thereby solved in that each spinning unit is provided, in the region of the ends of the friction rollers opposite of the withdrawal device, with a guide element to fixedly hold the return guided yarn end for a start spinning process over the region of the mouth or opening of the fiber feed channel.
Through these measures, it is assured that the return guided yarn end takes an exact position and is maintained there before the actual start spinning process. Above all, it is facilitated that the start of the yarn withdrawal with a predetermined yarn tension is carried out so that also then the yarn end exhibits a definite position which is optimum for a quality high value connection.
In advantageous arrangements of the invention, a two jaw yarn clamp is provided as the guide element. A yarn clamp of this kind offers the advantage that the tensioning, which with the yarn end portion is held, can be adjusted very exactly to a desired value. In order at each spinning unit to adjust the yarn position exactly, it is furthermore advantageous if the yarn clamp is so connected at the spinning unit that its distance to the respective wedge slots is adjustable.
In further arrangements of the invention, it is provided that a suction nozzle serves as a yarn guide element, which suction nozzle is connected at an under pressure source and can suck the yarn end inside thereof. Thereby it is assured that also the yarn end is guidingly controlled over the fiber feed opening of the fiber feed channel. As an auxiliary it can be provided that the suction nozzle receives the yarn end and is connected at a curved shape under pressure line. If the yarn end is sufficiently far return guided, then the friction force is so large that the yarn can be held under excellent tensioning without requiring a yarn clamp.
In further arrangements of the invention, a servicing device is provided which is movable along the spinning machine and adjustable to the individual spinning units. The servicing device is provided with means for opening and closing the yarn clamp and/or with means for connecting and separating the suction nozzle with and from the under pressure source.
Through these arrangements, it is possible for the start spinning procedure to be fully automated, including the preliminary steps to the actual start spinning procedure.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.